a) Field of the Invention
The present invention relates to a compact zoom lens system which has a high vari-focal ratio and a zooming range covering a super wide angle.
b) Description of the Prior Art
In the recent years, there are increasingly used fully automated cameras which have multiple functions in portable mechanical structures and are equipped with zoom lens systems. Further, these zoom lens systems for cameras are generally designed so as to widen photographic ranges.
It is desirable for shortening the total length of the zoom lens system of this type to select the refractive power distribution of the telephoto type lens system which enables to locate the lens system close to the image surface and design the lens system compact. However, the conventional zoom lens systems are mostly designed so as to have a sufficiently broad zooming range on the side of the tele positions as exemplified by the zoom lens system disclosed by U.S. Pat. No. 4,822,152 which has a high vari-focal ratio but is designed for a field angle on the order of 63.degree. at widest at the wide position. When an attempt is made to widen a field angle at the wide position of a zoom lens system which is of the telephoto type in the refractive power distribution thereof, back focal length of the zoom lens system is extremely shortened at the wide position, thereby enlarging diameter of the lens system and aggravating flare due to reflections on lens surfaces. Further, distortion and sagittal coma are aggravated by widening the field angle and can hardly be corrected.
For these reasons, there has been developed no compact zoom lens systems for cameras which has a field angle at the wide position as wide as that of the super wide-angle lens system for single-lens reflex cameras.